參數(shù)資料
型號： LTC3878IGN#TRPBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, PDSO16
封裝： 0.150 INCH, LEAD FREE, PLASTIC, SSOP-16
文件頁數(shù)： 8/26頁
文件大?。?/td> 399K
代理商： LTC3878IGN#TRPBF
LTC3878
3878fa
applicaTions inForMaTion
RegulatoroutputcurrentisnegativewhenITHisbetween
0Vand0.8VandpositivewhenITHisbetween0.8Vandthe
maximumfull-scaleset-pointof2.4V.Innormaloperating
conditionstheRUN/SSpinwillcontinuetochargepositive
untilthevoltageisequaltoINTVCC.
INTVCCUndervoltageLockout
WheneverINTVCCdropsbelowapproximately3.4V,the
deviceentersundervoltagelockout(UVLO).InaUVLO
condition,theswitchingoutputsTGandBGaredisabled.
Atthesametime,theRUN/SSpinispulleddownfrom
INTVCC to 0.8V with a 3A current source. When the
INTVCCUVLOconditionisremoved,RUN/SSrampsfrom
0.8Vandbeginsanormalcurrentlimitedsoft-start.This
featureisimportantwhenregulatorstart-upisnotiniti-
atedbyapplyingalogicdrivetoRUN/SS.Soft-startfrom
INTVCCUVLOreleasegreatlyreducesthepossibilityfor
start-uposcillationscausedbytheregulatorstartingup
atINTVCC(UVLOR)andthenshuttingdownatINTVCC(UVLO)
duetoinrushcurrent.
EfficiencyConsiderations
Thepercentefficiencyofaswitchingregulatorisequalto
theoutputpowerdividedbytheinputpowertimes100%.
Itisoftenusefultoanalyzeindividuallossestodetermine
whatislimitingtheefficiencyandwhichchangewould
producethemostimprovement.Althoughalldissipative
elementsinthecircuitproducelosses,fourmainsources
accountformostofthelossesinLTC3878circuits.
1.DCI2Rlosses.Thesearisefromtheresistancesofthe
MOSFETs,inductorandPCboardtracesandcausethe
efficiencytodropathighoutputcurrents.Incontinuous
modetheaverageoutputcurrentflowsthoughtheinductor
L,butischoppedbetweenthetopandbottomMOSFETs.
IfthetwoMOSFETshaveapproximatelythesameRDS(ON),
thentheresistanceofoneMOSFETcansimplybysummed
withtheresistancesofLandtheboardtracestoobtain
theDCI2Rloss.Forexample,ifRDS(ON)=0.01Ωand
RL=0.005Ω,thelosswillrangefrom15mWto1.5Was
theoutputcurrentvariesfrom1Ato10A.
2.Transitionloss.Thislossarisesfromthebriefamount
oftimethetopMOSFETspendsinthesaturatedregion
during switch node transitions. It depends upon the
inputvoltage,loadcurrent,driverstrengthandMOSFET
capacitance,amongotherfactors.Thelossissignificant
atinputvoltagesabove20V.
3.INTVCCcurrent.ThisisthesumoftheMOSFETdriver
andcontrolcurrents.
4.CINloss.Theinputcapacitorhasthedifficultjoboffilter-
ingthelargeRMSinputcurrenttotheregulator.Itmusthave
averylowESRtominimizetheACI2Rlossandsufficient
capacitancetopreventtheRMScurrentfromcausingad-
ditionalupstreamlossesinfusesorbatteries.
Otherlosses,whichincludetheCOUTESRloss,bottom
MOSFET reverse recovery loss and inductor core loss
generallyaccountforlessthan2%additionalloss.
Whenmakingadjustmentstoimproveefficiency,theinput
currentisthebestindicatorofchangesinefficiency.Ifyou
makeachangeandtheinputcurrentdecreases,thenthe
efficiencyhasincreased.Ifthereisnochangeininput
currentthereisnochangeinefficiency.
CheckingTransientResponse
Theregulatorloopresponsecanbecheckedbylooking
attheloadtransientresponse.Switchingregulatorstake
severalcyclestorespondtoastepinloadcurrent.When
aloadstepoccurs,VOUTimmediatelyshiftsbyanamount
equalto
ILOAD(ESR),whereESRistheeffectiveseries
resistanceofCOUT.ILOADalsobeginstochargeordis-
chargeCOUT,generatingafeedbackerrorsignalusedbythe
regulatortoreturnVOUTtoitssteady-statevalue.During
thisrecoverytime,VOUTcanbemonitoredforovershoot
orringingthatwouldindicateastabilityproblem.TheITH
pinexternalcomponentsshownintheDesignExamplewill
provideadequatecompensationformostapplications.
Aroughcompensationcheckcanbemadebycalculating
thegaincrossoverfrequency,fGCO.gm(EA)istheerror
amplifiertransconductance,RCisthecompensationre-
sistorandfeedbackdividerattenuationisassumedtobe
0.8V/VOUT.Thisequationassumesthatnofeed-forward
compensationisusedonfeedbackandthatCOUTsetsthe
dominantoutputpole.
f
g
R
I
C
V
GCO
m EA
C
LIMIT
OUT
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相關(guān)PDF資料
PDF描述
LTC3879EUD#TRPBF SWITCHING CONTROLLER, PQCC16
LTC3879IUD#PBF SWITCHING CONTROLLER, PQCC16
LTC3880IUJ-1#TRPBF 0.1 A DUAL SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC40
LTC3880IUJ#PBF 0.1 A DUAL SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC40
LTC3880EUJ-1#TRPBF 0.1 A DUAL SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC40
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC3879EMSE#PBF 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LTC3879EMSE#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LTC3879EUD#PBF 功能描述:IC REG CTRLR BUCK PWM CM 16-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LTC3879EUD#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 16-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LTC3879IMSE#PBF 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
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